Want to send a message directly to Facebook founder Mark Zuckerberg? It might cost you $100, if you don't want it to wind up in his spam folder.

If you're not already friends with Zuckerberg on the social network, you might see a pop-up asking you whether you'd like to pay $100 for your message to be sent straight to his inbox. If not, your missive goes to the "other" folder.

The steep fee is part of an experiment announced by the social network late last month -- apparently, it's only a small group of users that's being given the option of paid messaging. For everyone else, the system works just as before, with messages sent to non-friends routed to "other." (I tried this Friday morning, and my message went straight through, I assume, to Zuckerberg's "other" folder, since I'm not friends with him.)

The idea, Facebook said in an official blog post, is to try and reduce spam by making it difficult for mass messages to be sent to main inboxes. Even a nominal charge could spike the cost of spam campaigns to prohibitive heights. The social network called it a "small experiment to test the usefulness of economic signals to determine relevance."

According to Mashable, a company spokesperson has said that "we are testing some extreme price points to see what works to filter spam." In most cases, the fee is $1, and Facebook has also limited the number of messages that can be "prioritized" in this manner to one per week.

Email Jon Gold at jgold@nww.com and follow him on Twitter at @NWWJonGold.